The invention relates generally to a latch mechanism for an implement connected to a work vehicle, such as, for example, a bucket connected to a skid steer loader. More particularly, the invention relates to an improved hydraulic circuit for operating a hydraulic latch mechanism for securing an implement to the pivoting lift arms of a work vehicle, wherein the latch mechanism includes a solenoid operated hydraulic latch valve with integral sequence valve mechanism for operating a latch cylinder that moves the latch pin.
In the art of manufacturing work vehicles such as skid steer loaders, tractors, etc. that are constructed to have pivoting lift arms or booms attached at one end to the body of the vehicle, it is known that a coupler is often used to attach an implement to the distal end of the lifting arms or booms. The coupler serves as a connector to which an implement is operationally connected; however, in some vehicles the implement is connected directly to the distal end of the lifting arms or booms. In this manner, various implements such as a loader bucket, a grader, an auger, a broom, or other working implement attachment can be interchangeably connected to the work vehicle for the purpose of replacement, maintenance, or simply to change the implement attachment to meet the particular job requirement. In other words, for example, the coupler permits an operator to place a bucket on the work vehicle when digging is required, or a grader on the vehicle when earth leveling is desired, and so forth.
When the desired implement is connected to the coupler (also known as an xe2x80x9cimplement mounting platexe2x80x9d) or directly to the distal ends of the lifting arms, typically a latch pin mechanism is used to secure the implement in place. For example, U.S. Pat. No. 3,204,793 to Lane (specifically incorporated herein in its entirety by reference) discloses a front end loader that has an implement attachment apparatus that includes a pair of hydraulic cylinders for moving corresponding piston rods to lock an implement in operative engagement with a hitch member. Although hydraulic tubes are disclosed, the Lane Patent is silent with respect to what specific hydraulic mechanism is used for activating the hydraulic cylinders.
U.S. Pat. No. 3,203,565 to Keskitalo (specifically incorporated herein in its entirety by reference) discloses various latch mechanism structures for connecting a side dump bucket to a vehicle mounted loader. Each latch mechanism structure includes a hydraulic jack and cooperating locking rod that are used to selectively attach one or both bars of the bracket members to a cradle to prevent pivotal movement of the cradle. The cradle is supported by lifting arms that impart lifting and/or tilting movements to the cradle in a conventional manner. The cradle supports a dump bucket as is known in the art. Like Lane, the Keskitalo Patent is silent with respect to the hydraulic circuit that is used to operate the disclosed latch mechanism structure.
U.S. Pat. No. 6,132,131 to Nakamura et al. discloses an attachment mounting/demounting device for a work vehicle, wherein a bucket implement is connected to the boom of a work vehicle by means of the mounting/demounting device. The mounting/demounting device includes a rocker arm rocked by a mounting/demounting cylinder and a lock piston that is advanced or retracted depending upon the condition of a hydraulic circuit. The hydraulic circuit includes a selector valve connected to a hydraulic pump and an oil tank, and a 4/2 solenoid operated spring biased switching valve connected to the selector valve. The switching valve operates both the mounting/demounting cylinder and the lock piston, which incorporates the features of a pilot operated spring biased 2/2 valve.
In operation, the rocker arm and the lock piston move together to either secure the bucket implement or to release the bucket implement depending upon the state of the switching valve. Because the switching valve is electronically controlled by a single select switch, the mounting/demounting device disclosed by the Nakamura et al. Patent is prone to accidental activation. Furthermore, the hydraulic circuit of the device is separate from the other hydraulic systems used to operate the work vehicle, which is a drawback because the structure does not take advantage of other necessary hydraulic circuits. In other words, it would be more cost efficient to incorporate the hydraulic circuit of the mounting/demounting device into a previously existing hydraulic circuit such as for moving the boom.
A non-hydraulic latch pin mechanism is disclosed in U.S. Pat. No. 5,769,596 to Burton, wherein shiftable pins are moved into and out of a latching relation with the implement that is being attached to the work vehicle when an electrically powered linear actuator moves the shiftable pins. Such an electrically operated and powered latch pin mechanism has the drawback that it is relatively slow, places a drain on the vehicle""s electrical system, and requires the addition of an expensive electric motor for each shiftable pin.
U.S. Pat. No. 5,562,397 to Albright discloses another electric latch pin mechanism for attaching an attachment to an attachment frame of a skid steer loader, which shares many of the drawbacks of the mechanism disclosed by Burton. Albright suggests that a hydraulic actuator could be substituted for the electric motor driven power actuator on the attachment plate; however, Albright does not suggest all of the features of the hydraulic attachment latch mechanism in accordance with the present invention. U.S. Pat. No. 5,562,397 to Albright is also incorporated herein by reference in its entirety.
The present invention provides an improved hydraulic circuit for operating a hydraulic latch mechanism, wherein the latch mechanism includes a solenoid operated hydraulic latch valve with integral sequence valve for operating a latch cylinder that moves one or more latch pins. The present invention endeavors to overcome the drawbacks of the prior art latch mechanisms.
Accordingly, a primary object of the present invention is to overcome the disadvantages of the prior art latch mechanisms.
Another object of the present invention is to provide a latch mechanism that is incorporated into a hydraulic circuit for operating the lift arms of a work vehicle.
A further object of the present invention is to provide a latch mechanism that is incorporated into a hydraulic circuit for operating the mount plate tilt mechanism that is cost efficient to manufacture, easy to maintain, and durable because the structure minimizes the need for additional components such as extra hydraulic plumbing and electrical wiring.
A still further object of the present invention is to provide a latch mechanism that requires two simultaneous and conscious actions to be performed by the operator of the work vehicle in order to activate the latch mechanism to virtually eliminate the possibility of inadvertently activating the latch mechanism.
Yet another object of the present invention is to provide a latch mechanism that provides an over-center mechanism so that any loss of hydraulic pressure will have no effect on the security of the latch of the latch mechanism.
In accordance with the above objectives, the present invention provides a work vehicle characterized by: (1) at least one implement lifting arm connectable to an implement and (2) a hydraulic implement circuit for powering the implement, the hydraulic implement circuit having a hydraulic pump and a hydraulic fluid reservoir connected to hydraulic conduits of the hydraulic implement circuit, wherein the hydraulic pump is connected to pump hydraulic fluid from the reservoir through the conduits of the hydraulic implement circuit, wherein the implement circuit further comprises: (3) at least one hydraulic implement cylinder for maneuvering the implement, the at least one implement cylinder being connected to the conduits of the implement circuit so as to be powered by the hydraulic pump; and (4) a latch mechanism comprising a latch valve with integral sequence valve mechanism and a latch cylinder, wherein the latch valve is connected to receive hydraulic fluid from the at least one implement cylinder, and the latch cylinder is connected to receive hydraulic fluid from the latch valve, wherein the latch mechanism operates to securely connect the implement at one end of the at least one lifting arm when the at least one implement cylinder is in a first state and the latch valve is operated to direct hydraulic fluid to the latch cylinder.
In a second preferred embodiment of the invention, the first preferred embodiment is modified so that the first state is a fully retracted state.
In a third preferred embodiment of the invention, the first preferred embodiment is modified so that the latch valve is disposed along a coupler.
In a fourth preferred embodiment of the invention, the first preferred embodiment is modified so that the latch valve is a solenoid activated spool valve with integral sequence valve.
In a fifth preferred embodiment of the invention, the first preferred embodiment is modified so that the latch valve is a solenoid-operated, spring-biased 4/3 spool valve mechanism in parallel with a sequence valve mechanism.
In a sixth preferred embodiment of the invention, the first preferred embodiment is modified so that the latch cylinder has a piston that moves into an extended position when the latch mechanism operates to securely connect the implement at one end of the at least one lifting arm.
In a seventh preferred embodiment of the invention, the sixth preferred embodiment is modified so that at least one remote latch pin is mechanically connected to the piston so that the at least one remote latch pin moves into an extended position to securely connect the implement at one end of the at least one lifting arm when the piston moves into the extended position.
In an eighth preferred embodiment of the invention, the sixth preferred embodiment is modified so that two remote latch pins are mechanically connected by a connection assembly to the piston so that each remote latch pin moves into an extended position to securely connect the implement at one end of the at least one lifting arm when the piston moves into the extended position.
In an ninth preferred embodiment of the invention, the seventh preferred embodiment is modified so that the latch mechanism includes a first lever arm connected to the piston and a second lever arm connected to the base end of the latch cylinder so that the at least one remote latch pin is maintained in the extended position when the latch cylinder is relaxed.
In a tenth preferred embodiment of the invention, a hydraulic circuit for a work vehicle is characterized by (1) a hydraulic pump and a hydraulic fluid reservoir connected to hydraulic conduits of the hydraulic implement circuit, wherein the hydraulic pump is connected to pump hydraulic fluid from the reservoir through the conduits of the hydraulic implement circuit; (2) a first hydraulic implement cylinder arranged to maneuver the implement, the first implement cylinder being connected to the conduits of the implement circuit so as to be powered by the hydraulic pump; and (3) a latch mechanism including a latch valve with integral sequence valve mechanism and a latch cylinder, wherein the latch valve is connected to receive hydraulic fluid from the at least one implement cylinder, and the latch cylinder is connected to receive hydraulic fluid from the latch valve, wherein the latch mechanism operates to position a latching when the at least one implement cylinder is in a first state and the latch valve is operated to direct hydraulic fluid to the latch cylinder.
In an eleventh preferred embodiment of the present invention, the tenth preferred embodiment is modified so that the hydraulic circuit is hydraulically connected to a main hydraulic circuit of the work vehicle so that the pump and the reservoir are connected to and are part of the main hydraulic circuit.
The tenth preferred embodiment of the invention can be further modified in a manner in accordance with the various modifications of the first preferred embodiment of the invention.
In a twelfth preferred embodiment of the invention, a hydraulic latch mechanism hydraulically connectable to a hydraulic circuit of a work vehicle, wherein the hydraulic circuit is connectable to provide hydraulic fluid to power the hydraulic latch mechanism, is characterized by (a) a solenoid-activated latch valve with integral sequence valve mechanism wherein the latch valve includes an intake connectable to receive hydraulic fluid from the hydraulic circuit so that the integral sequence valve mechanism senses hydraulic pressure load provided by the hydraulic circuit to the intake; and (b) a hydraulic latch cylinder connected to receive hydraulic fluid from the latch valve so that (1) when hydraulic pressure load provided by the hydraulic circuit to the intake exceeds a minimum threshold pressure load and (2) when a solenoid mechanism of the latch valve is selectively activated, then hydraulic fluid is directed by the latch valve to the latch cylinder to activate the latch cylinder to extend a first pin to a latching position.
In a thirteenth preferred embodiment of the invention, the twelfth preferred embodiment is modified so that the first pin is mechanically connected by a connection assembly to two remote pins so that when the first pin extends, the two remote pins extend simultaneously to a latching position.
In a fourteenth preferred embodiment of the invention, the twelfth preferred embodiment is modified so that the minimum threshold pressure load is exceeded when at least one implement cylinder of the hydraulic circuit is in a fully retracted state.
In a fifteenth preferred embodiment of the invention, the twelfth preferred embodiment is modified so that the latch valve and the latch cylinder are disposed along a mount.
Further objects, features and advantages of the present invention will become apparent from the Detailed Description of Preferred Embodiments, which follows, when considered together with the attached drawings.